1. Field of the Invention
The present invention relates to an infuser for continuously infusing predetermined volume of a solution of medicine into the human body within a predetermined period of time.
2. Description of the Related Art
There are two conventional methods of infusing a solution of medicine into the human body over a relatively long period of time: in one method, the solution of medicine is injected from an injecting needle or catheter, which is attached to a syringe containing the solution of medicine, by operating the syringe manually, electrically or by utilizing the action of a spring; and in the other method, an installation bottle containing the solution of medicine is used, and the solution is caused to drop therefrom under gravity or in an electrical manner.
In a case where the solution of medicine is infused into the human body over from a few minutes to a few hours, an injecting needle of a catheter must be kept attached to a syringe or instillation bottle serving as a medicine supplier, and this causes great inconvenience to the operator as well as to the patient.
For instance, in a case where an infusion is continuously carried out in a manual fashion, the movement of both the patient and the operator is restricted for a certain period of time, and this gives them great pains mentally and physically. It is generally believed that people can remain in the same posture only for 1 or 2 minutes under such a condition. In contrast, in a case where the infusion of the solution of medicine is carried out electrically or by utilizing the action of a spring, a power source must be secured near the infusion site, and a syringe must properly be placed. This also restricts the action of the patient.
In addition, when the solution of medicine is continuously infused into the human body by utilizing the instillation method, a comparatively large amount of a supplemental liquid relative to the medicine needs to be used, and even if the patient does not require such a supplemental liquid, he/she must be subjected to the infusion of the same. Moreover, an instillation bottle or container must be placed at a position higher than where the patient is lying, and a complicated and long conduit is required to connect the injecting needle or catheter to the instillation bottle. This also restricts the movement of the patient, and the operator is required to confirm whether or not the instillation of the solution of medicine is being carried out properly.
Japanese Patent Publication No. 45799/1980 discloses a flow control device for use in infusing a solution of medicine into the human body. In this device, a core having a spiral groove formed therein is inserted in a sleeve, and this sleeve is clamped by means of a ring so as to control the flow of the solution. However, with this flow control device, it is not possible to continuously infuse the solution of medicine over a long period of time.
U.S. Pat. No. 4,318,400 discloses an infuser for continuously infusing a solution of medicine. In this infuser, a balloon containing therein the solution of medicine is inserted in a cylinder, and the balloon contracts in the axial direction with the solution of medicine contained therein being injected therefrom by virtue of the contracting action of the balloon. However, this infuser is disadvantageous in that the solution contained in the balloon cannot completely be discharged therefrom.
In view of the above drawbacks, the present applicant has previously developed "An Infuser with a Balloon for Continuously Infusing a Solution of Medicine" (Japanese Patent No. 1384289) for infusion into the human body over a comparatively long period of time and which has a simple structure is easy to handle and is reliably safe.
This patented infuser comprises a tubular main body having a flow path that extends formed along the longitudinal axis of the tubular main body, a portion with a check valve provided at one end of the tubular main body to allow the solution of medicine to be infused therefrom into the tubular main body, a portion provided at the other end of the tubular main body to allow a solution of medicine to be injected therefrom, a member provided at an intermediate position along the length of the tubular main body to shut off the flow path, an inlet hole and an outlet hole (or outlet hole with a fine porous membrane) provided in the neighborhood of the shut off member on the medicine infused portion side and medicine injecting portion side, respectively, in such a manner as to extend through the wall of the tubular main body, and a balloon made from an elastic material and surrounding the inlet and outlet holes, the balloon being air-tightly secured to the outer periphery of the tubular main body at the perimeter thereof.
In addition, the present applicant has also previously disclosed "An Infuser with a Balloon for Continuously Infusing a Solution of Medicine into a Blood Vessel" (the official Gazette of Japanese Patent Public Disclosure No. 11465/1987) which comprises the above patented infuser and an intravascular retainer connected to the medicine injecting portion of the same infuser.
Moreover, the applicant of the present invention also previously disclosed "An Infusing Catheter for Continuously Infusing a Solution of Medicine into a Urinary Bladder" (the Official Gazette of Japanese Patent Public Disclosure No. 11464/1987) that is intended to be used when continuously infusing a solution of medicine into the human body over a comparatively long period of time and which has a simple structure, is easy to handle and is safe to use.
In this catheter, a conventional common catheter for a urinary bladder is employed, and a recess is formed in a part of the outer periphery of the catheter at the proximate end thereof. A balloon made from an elastic material is provided on the catheter so as to surround the recess, and the balloon is air-tightly secured to the outer periphery of the catheter at the perimeter thereof. A capillary tube is provided on the wall of the catheter along the longitudinal axis thereof. This capillary tube is open at the proximate end thereof so as to form an outlet port for a solution of medicine and is caused to communicate with the recess at the proximate end. A portion allowing the solution of medicine to be infused therefrom into the balloon is air-tightly secured to the balloon at the central portion thereof, and a central passageway is provided at the center of the portion allowing the medicine to be infused. A valve is provided on the central passageway at the inlet end thereof, and the passageway communicates with the recess at the outlet end thereof.
The above-described infuser or catheter is provided with a capillary hole or capillary tube for controlling the time during which the solution of medicine is allowed to flow out. It is, however, difficult to actually form such a capillary hole or capillary tube, and even if this is possible, they are readily clogged with foreign matters.
In view of the above drawbacks, the present applicant succeeded in contriving a method of forming a capillary tube for controlling the time during which the solution of medicine is allowed to flow out with ease and previously disclosed "An Infuser with a Balloon for Continuously Infusing a Solution of Medicine" having a structure in which the clogging of a capillary tube is prevented (PCT-JP-88-01055).
This infuser comprises a tubular main body having a flow path that is formed along the longitudinal axis of the tubular main body. This tubular main body is provided at one end thereof with a portion with a check valve allowing the solution of medicine to be infused therefrom into the tubular main body and at the other end thereof with a portion allowing the solution of medicine to be injected therefrom. A predetermined volume of a normal temperature or thermosetting pourable resin that exhibits no adhesiveness relative to a specific material fills the other end of the tubular main body, and a linear, spiral or wound capillary wire made from a specific material and having a predetermined diameter is embedded in the pourable resin. This capillary wire extends into the tubular main body at one end thereof, and the other end thereof is guided so as to extend through the medicine injecting portion to the outside of the tubular main body. Holes are formed in the tubular main body in such a manner as to extend through the wall thereof, and a balloon made from an elastic material is provided so as to surround the holes with a circumferential portion thereof being air-tightly fixed to the outer periphery of the tubular main body.
The capillary wire is drawn to the outside of the tubular main body so as to form a capillary hole through the pourable resin portion, and an indwelling retainer for the human body can be fitted to the medicine injecting portion.
This medicine infuser, however, has a drawback in that minute burrs are formed on the inner surface of the capillary hole after the capillary wire has been drawn out. Thus, it is difficult to form a hole which will function steadily.
The present applicant has also disclosed "An Infuser with a Balloon for Continuously Infusing a Solution of Medicine" in which the time during which the solution of medicine is allowed to flow out is able to be variously changed and which has a steady capillary hole through which the solution of medicine is allowed to flow out (PCT-JP-89-00515).
This infuser comprises a tubular main body having a flow path that extends along the longitudinal axis of the tubular main body. This tubular main body is provided at one end thereof with a portion with a check valve or one-way cock allowing the solution of medicine to be infused therefrom into the tubular main body and at the other end thereof with a portion allowing the solution of medicine to be injected therefrom. A control portion for controlling the outflow of the solution of medicine is also provided adjacent to the medicine infused portion at the other end of the tubular main body. A plurality of holes are formed in the tubular main body in such a manner as to extend through the wall thereof, and a balloon made from an elastic material is provided so as to surround the holes with a circumferential portion thereof being air-tightly fixed to the outer periphery of the tubular main body.
In the infuser with a balloon for continuously infusing a solution of medicine developed by the present applicant, however, a rate of expansion and contraction of the balloon is different between a center portion and both end portions thereof, since the circumferential end portions of the balloon are secured to the tubular main body. Consequently, the solution of medicine flows under a high pressure and flow rate at the beginning of ejection while the solution flows under a low pressure and flow rate at the end of the ejection.